Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $95.27   11.821%   $106.5319   $106.53   $106.55   $106.50  
  Purchase #2 $53.92   5.532%   $56.9029   $56.90   $56.90   $56.90  
  Purchase #3 $12.40   9.147%   $13.5342   $13.53   $13.55   $13.50  
  Purchase #4 $150.34   8.871%   $163.6767   $163.68   $163.70   $163.70  
  Purchase #5 $93.80   12.532%   $105.555   $105.56   $105.55   $105.60  
  Purchase #6 $175.31   4.353%   $182.9412   $182.94   $182.95   $182.90  
  Purchase #7 $126.98   3.747%   $131.7379   $131.74   $131.75   $131.70  
  7 purchase totals = $708.02       $760.8798   $760.88   $760.95   $760.80